For the production of alloy powders by grinding pieces of a suitable, previously prepared alloy which contains an active metal, e.g., titanium, a process is described in "Titanium Science and Technology--Proceedings of the Fifth International Conference on Titanium", Vol 1, Munich, Sept. 1984, pp. 443 to 450, which is called "Hydride Dehydriding Process" (HDH) and in which coarse pieces of a selected active brazing alloy, particularly Ti6Al4V, are prehydrogenated and then pulverized. Thereafter the powder is carefully dehydrogenated.
The dehydrogenation before the grinding operation increases the brittleness of the coarse pieces and therefore improves their grindability. Hydrogen is adsorbed at the grain boundaries of the polycrystalline pieces until the latter are saturated with hydrogen.
Pulverizing mills, so-called colloid mills, are commercially available in which an inert gas, particularly hydrogen, is supplied to the material being ground.
If an active brazing powder obtained and dehydrogenated by the above HDH process is used to produce an active brazing paste, it must be miscible with an organic material acting as a vehicle and processible openly, i.e., under normal atmospheric and temperature conditions. Dehydrogenated active brazing powder, however, is susceptible to the adsorption of components of air, i.e., particularly of oxygen, water vapor, nitrogen and/or carbon dioxide, but also to the adsorption of C--H compounds stemming from the organic vehicle.
In a variant of the production of electrically conductive interface connections through insulating parts, particularly ceramic pressure sensors, a metal lead is inserted into a hole of the insulating part and surrounded by a bulge of active brazing paste which is subsequently vacuum-brazed with the insulating part and the lead at a high temperature, see EP-A-516 579 (=U.S. Ser. No. 07/981,781, Canadian Appln. No. 2,066,325).
It has turned out, however, that because of the absorptions mentioned above, an active brazing paste made from dehydrogenated active brazing powder is not suited for brazing such leads in place.
It is, therefore, the object of the invention to provide a method of producing an active brazing paste which does not have this disadvantage.